EP1966294B1 - Polyamide molding materials - Google Patents

Abstract

Use of a succinic acid ester compound (I) as a molecular weight reducing additives for the preparation of polyamide molded mass. Use of a succinic acid ester compound (I) of formula (R-(O-C(=O)-Y 1>-C(=O)-OH) n), as a molecular weight reducing additives for the preparation of polyamide molded mass. R, Y 1>1-30C aliphatic or aromatic carbon further optionally with an heteroatom such as N, O, S or P; and n : 1-20. Independent claims are included for: (1) a polyamide molded material comprising at least a polyamide with a relative solution viscosity of 2.6-3.2 in m-cresol, and (I); and (2) a method for the preparation of the polyamide molded mass comprising melt mixing the polyamide and (I) in a multi-shaft extruder.

Description

The invention relates to the use of monoesters of succinic acid as a molecular weight-degrading additive for improving the flowability in the production of polyamide molding compositions.

Polyamides are characterized by a variety of advantageous properties, e.g. high toughness, high temperature resistance u.a. which secure their place in the market in the field of engineering thermoplastics. These basic properties of the polymer resin are generally modified by the addition of additives. Polymer resin and additive together give the so-called molding compound. For mechanical property improvement of polyamide, fillers such as glass fibers, wollastonite, kaolin or talc are often added to the base polymer resin, for example, by a melt extrusion method. Polyamide molding compounds are used in many applications. Examples include injection molded parts z. For the automotive market.

However, the fillers used in the molding compositions can lead to a considerable increase in the melt viscosity of the molding compositions and thus limit the flowability of these molding compositions. However, a high flowability is advantageous for the uniform and complete filling of a mold, as well as for short cycle times and low filling pressures in injection molding. One way to ensure the high flowability of the polyamide molding compounds in the injection molding, is the use of polyamide resins with the lowest possible melt viscosity.

In general, polyamide resins show a decreasing melt viscosity as the molecular weight decreases. It therefore makes sense to use a polyamide base resin which has a reduced molecular weight for the applications where high flowability of the molding composition is advantageous or necessary.

However, from the point of view of the industrial production of polyamides, this is disadvantageous, since it means the use of an additional base resin, which is associated with increased logistical and economic costs. On an industrial scale, polyamide 6 base resin is preferably produced in a continuous process by feeding liquid caprolactam with about 1-4% water from above to one or a series of vertical tubular reactors. The polymerization is carried out at temperatures between 240 ° C and 270 ° C and a residence time of 1 to 30 hours. This means very long lead and lag times for product changes, which makes the process economically and ecologically disadvantaged. Furthermore, the melt stiffness is reduced in low molecular weight polyamides, which is for example when used Conventional strand granulation reduces the overall production capacity by reducing the pull-off speeds due to the risk of strand breakage.

It is therefore advantageous to produce polyamide molding compositions with improved flowability based on polyamide resins having a customary average molecular weight. Polyamides of conventional average molecular weight are understood to mean aliphatic polyamides which have a relative solution viscosity of 2.9 +/- 0.3 in meta-cresol (1.0% solution, 25 ° C.).

Polyamide molding compositions are generally produced by a melt-extrusion process or compounding process, wherein the polyamide resin is melted in an extruder and optionally mixed with further additives. Fillers and / or reinforcing materials such as glass fibers are usually metered into the polymer melt via a separate metering funnel. The resulting polyamide molding compound is extruded as a strand, cooled and granulated. The granules are then further processed by further processing steps, such as injection molding, to form parts or semi-finished products.

It is possible to influence the molecular properties of the polymer resin via the addition of additives during an extrusion process. So is in the patent application EP 0672703 A1 describes a process for the preparation of star-branched polyamide resins, wherein tri- or higher-functional amines are added as additives to a polyamide melt during an extrusion process.

It is known from the prior art that by adding acids as additives during an extrusion process, it is possible to achieve flowabilities of molding compositions which are normally obtained only with polyamide resins of reduced molecular weight.

In the patent US 6,835,771 B2 For example, dicarboxylic acids such as sebacic acid are added during the compounding step to reduce the viscosity.

WO 03/060001 A2 describes the use of ortho-hydroxytriazines, (sterically) hindered hydroxybenzoates and optionally (sterically) hindered amines as UV stabilizers, inter alia, in polymaiden.

US 6,376,584 B1 describes the use of (sterically) hindered amines which are substituted on the N atom by N-alkoxy groups and have 1 to 3 hydroxyl groups as antistatic agents in polycarbonates and polycarbonate / ABS blends. Furthermore, this document teaches the use of these compounds in Polymaid / EPDM blends.

WO 03/01159 A discloses degradable compositions of biodegradable aliphatic-aromatic copolyesters and a plasticizer, preferably esters of citric acid, which Benzoic acid or mixtures thereof, inter alia, for use in polyether-polyamide block copolymers.

US Pat. No. 6,423,768 B1 describes the improvement of polymer organoclay compositions, inter alia based on polyamide. Dicarboxylic acids, tricarboxylic acids and cyclic carboxylic anhydrides, including 2-hydroxysuccinic anhydride, are used.

WO 01/94464 A teaches improving the viscosity properties of plastisols for use as adhesives in automotive manufacturing. Plasticizers include monomeric esters of succinic acid.

WO 99/46323 discloses the avoidance of discoloration of nylon under the influence of light or the influence of heat by the use of, inter alia, aliphatic dicarboxylic acids.

EP 0 469 542 A2 describes polyamide compositions having a flow modifier. As examples, methyl- or bromine-substituted succinic acid as well as succinic anhydride are listed.

EP 0 516 150 A1 discloses compositions based on A) poly (phenylene) ethers, B) polyamide and C) alkenyl succinic anhydride.

However, the molecular weight reduction may take place only in the preparation of the polyamide molding composition and must be completed as far as possible before the subsequent processing steps of the molding composition. In particular, in the subsequent processing by injection molding at melt temperatures which are in the range of temperatures in the preparation of the molding composition further degradation of the resin is undesirable. The further reduction in the molecular weight of the molding compound in the processing steps following the compounding is undesirable because this leads to a non-reproducible behavior during the processing of the molding compound and, moreover, can impair the mechanical properties of the molding compound.

• aus Polyamidharzen mit einem herkömmlichen Molekulargewicht, d. h. Polyamidharze mit einer relativen Lösungsviskosität in m-Kresol von 2,6 bis 3,2 hergestellt werden, und
• mechanische und rheologische Eigenschaften aufweisen, die vergleichbar sind, mit den mechanischen und rheologischen Eigenschaften von leichtfließenden Formmassen, die aus einem Polyamidharz mit einem verringerten Molekulargewicht hergestellt sind, d. h. um weniger als 10 % von diesen abweichen,
• verarbeitungsstabil sind, d. h. deren relative Lösungsviskosität in einem mittels Spritzgussverfahren hergestellten Formteil maximal nur 5 % geringer ist, als die relative Lösungsviskosität des Polyamidharzes im Ausgangsmaterial.

Object of the present invention was therefore to provide easy-flowing polyamide molding compositions which:

• of polyamide resins having a conventional molecular weight, ie, polyamide resins having a relative solution viscosity in m -cresol of 2.6 to 3.2, and
• have mechanical and rheological properties comparable to the mechanical and rheological properties of easily flowing molding compounds prepared from, ie less than 10% of, a polyamide resin of reduced molecular weight;
• are stable to processing, ie their relative solution viscosity in a molded part produced by injection molding is only 5% less than the relative solution viscosity of the polyamide resin in the starting material.

The solution to this problem and thus the subject of the invention is the use of mono-esters of succinic acid as a molecular weight-degrading additive for improving the flowability in the production of polyamide molding compositions.

Surprisingly, the mono-esters of succinic acid are particularly suitable as molecular weight-reducing additives in the production of polyamide molding compositions by extrusion, by leading to a reduction of the relative solution viscosity of the polyamide resin and thus significantly improve its flowability. In addition, the molecular weight degrading effect of the mono-esters of succinic acid is largely limited to the extrusion step, and, for example, in the subsequent injection molding step, there is no further significant reduction in the relative solution viscosity of the polyamide resin to use other carboxylic acid compounds.

In a preferred embodiment, in addition to the components A) polyamide and B) mono-esters of succinic acid, the components C) and / or D) can be added.

The relative solution viscosity is determined according to ISO 307: 2003 and is applicable to polyamides designated PA 46, PA 6, PA 66, PA 69, PA 610, PA 612, PA 11, PA 12, PA 6T and PA MXD6.

As component A), the compositions to be improved in their flowability comprise at least one partially crystalline thermoplastic polyamide having a relative solution viscosity in m-cresol of from 2.6 to 3.2, preferably from 99.9 to 10 parts by weight, more preferably 99, 0 to 55 parts by weight.

The polyamides to be improved in their fluidity according to the invention can be prepared by various processes and synthesized from very different building blocks and in special applications alone or in combination with processing aids, stabilizers, polymeric alloying partners (eg elastomers) or reinforcing materials (such as eg mineral fillers or glass fibers) to materials with specially adjusted property combinations. Also suitable are blends with shares of other polymers, eg. Example of polyethylene, polypropylene, ABS (acrylonitrile-butadiene-styrene copolymer), where appropriate, one or more compatibilizers can be used. The properties of the polyamides can be improved by adding elastomers, for. B. with regard to the impact strength of, for example, reinforced polyamides. The multitude of possible combinations enables a very large number of products with different properties.

For the production of polyamides, a variety of procedures have become known, depending on the desired end product different monomer units, different Chain regulators for setting a desired molecular weight or monomers with reactive groups for later intended post-treatments can be used.

The technically relevant processes for the preparation of polyamides usually run via the polycondensation in the melt. In this context, the hydrolytic polymerization of lactams is understood as a polycondensation.

According to the invention preferably used as component A) polyamides are partially crystalline polyamides, which can be prepared starting from diamines and dicarboxylic acid and / or lactams with at least 5 ring members or corresponding amino acids.

Suitable starting materials are aliphatic and / or aromatic dicarboxylic acids such as adipic acid, 2,2,4- and 2,4,4-trimethyladipic acid, azelaic acid, sebacic acid, isophthalic acid, terephthalic acid, aliphatic and / or aromatic diamines such as. As tetramethylenediamine, hexamethylenediamine, 1,9-nonanediamine, 2,2,4- and 2,4,4-trimethylhexamethylenediamine, the isomeric Diaminodicyclohexlmethane, Diaminodicyclohexylpropane, bis-aminomethyl-cyclohexane, phenylenediamines, xylylenediamines, aminocarboxylic acids such. B. aminocaproic acid, or the corresponding lactams into consideration. Copolyamides of several of the monomers mentioned are included.

Particularly preferred according to the invention are caprolactams, very particularly preferably ε-caprolactam, and most of the compounds based on PA6, PA66 and other aliphatic and / or aromatic polyamides or copolyamides in which 3 to 11 methylene groups are present on a polyamide group in the polymer chain.

The semicrystalline polyamides to be improved according to the invention as component A) in their flowability can also be used in a mixture with other polyamides and / or further polymers.

The polyamides conventional additives such. As mold release agents, stabilizers and / or flow aids are added in the melt or applied to the surface.

Preferably, the mono-esters of succinic acid to 0.1 to 2 wt .-%, particularly preferably used to 0.15 to 1.5 wt .-% based on the total amount of polyamide resin.

Especially preferred according to the invention are the mono-esters of succinic acid with aliphatic monohydric or polyhydric alcohols, for example succinic acid monomethyl ester, succinic acid monoethyl ester, monopropyl succinate, and ethylene glycol disuccinate, propylene glycol disuccinate, butylene glycol disuccinate, glycerol trisuccinate, pentaerythritol tetrasuccinate, dipentaerythritol hexasuccinate and tripentaerythritol octasuccinate.

• Bernsteinsäuremonomethylester,
• Pentaerythritoltetrasuccinat der Formel (II) aus DE-A 2 411 480 :
  

In particular, very particular preference is given to using:

• Bernsteinsäuremonomethylester,
• Pentaerythritol tetrasuccinate of the formula (II) DE-A 2 411 480 :
  

Dipentaerythritolhexasuccinate of the formula (III) WO 2005 090441 A1

• A) Füllstoffe und/oder Verstärkungsstoffe wie z. B. Minerale, synthetische Fasern, Glasfasern, Whisker oder Kohlenstofffasem. Als verstärkendes Additiv werden Additive verstanden, die das Zug-Modul der Formmasse erhöhen. Als faserförmige Verstärkungsstoffe neben Glasfasern kommen Aramidfasern, Mineralfasern und Whisker in Betracht. Als geeignete mineralische Füllstoffe seien beispielhaft Kalziumcarbonat, Dolomit, Kalziumsulfat, Glimmer, Fluorglimmer, Wollastonit, Talkum und Kaolin genannt. Zur Verbesserung der mechanischen Eigenschaften können die faserförmige Verstärkungsstoffe und die mineralischen Füllstoffe oberflächenbehandelt sein.
• D) weitere Additive und Hilfsstoffe wie beispielsweise Flammschutzmittel, Elastomermodifikatoren, Farbmittel, Gleit- und Entformungsmittel oder Nukleirungsmittel. Als Gleit und Entformungsmittel können beispielsweise Esterwachse, Pentaerytritoltetrastearat (PETS), langkettige Fettsäuren (z.B. Stearinsäure oder Behensäure), deren Salze (z.B. Ca- oder Zn-Stearat) sowie Amidderivate (z.B. Ethylen-bis-stearylamid) oder Montanwachse (Mischungen aus geradkettigen, gesättigten Carbonsäuren mit Kettenlängen von 28 bis 32 C Atomen) eingesetzt werden. Erfindungsgemäß werden bevorzugt Gleit- und/oder Entformungsmittel aus der Gruppe der Ester oder Amide gesättigter oder ungesättigter aliphatischer Carbonsäuren mit 8 bis 40 C-Atomen mit aliphatischen gesättigten Alkoholen oder Aminen mit 2 bis 40 C-Atomen eingesetzt, wobei Ethylen-bis-stearylamid oder Pentaerythrittetrastearat (PETS) ganz besonders bevorzugt sind.

As already mentioned above, the polyamide molding compositions to be improved according to the invention in their flowability can furthermore contain:

• A) fillers and / or reinforcing agents such. As minerals, synthetic fibers, glass fibers, whiskers or carbon fibers. As a reinforcing additive additives are understood that increase the tensile modulus of the molding material. As fibrous reinforcing materials in addition to glass fibers are aramid fibers, mineral fibers and whiskers into consideration. Examples of suitable mineral fillers are calcium carbonate, dolomite, calcium sulfate, mica, fluoromica, wollastonite, talc and kaolin. To improve the mechanical properties, the fibrous reinforcing materials and the mineral fillers may be surface-treated.
• D) other additives and auxiliaries such as flame retardants, elastomer modifiers, colorants, lubricants and mold release agents or nucleating agents. Examples of lubricants and mold release agents include ester waxes, pentaerythritol tetrastearate (PETS), long-chain fatty acids (eg stearic acid or behenic acid), their salts (eg Ca or Zn stearate) and amide derivatives (eg ethylene-bis-stearylamide) or montan waxes (mixtures of straight-chain, saturated carboxylic acids with chain lengths of 28 to 32 C atoms) can be used. Lubricants and / or mold release agents from the group of esters or amides of saturated or unsaturated aliphatic carboxylic acids having 8 to 40 carbon atoms with aliphatic are preferably used according to the invention saturated alcohols or amines having 2 to 40 carbon atoms, with ethylene-bis-stearylamide or pentaerythritol tetrastearate (PETS) are very particularly preferred.

As plasticizers, for example, dioctyl phthalate, dibenzyl phthalate, butyl benzyl phthalate, hydrocarbon oils, N- (n-butyl) benzenesulfonamide can be used.

Suitable colorants are both organic and inorganic pigments and / or dyes. Carbon black is optionally present in very small amounts as part of the pigment mixture. If appropriate, the pigments / dyes and / or carbon blacks can also be used as a batch.

Examples of inorganic pigments are antimony trioxide, antimony pentoxide, basic lead carbonate, basic lead sulfate or lead silicate, lithopones, titanium dioxide (anatase, rutile), zinc oxide, zinc sulfide, metal oxides such as Berliner blue, lead chromate, lead sulfochromates, chromium antimony titanate, chromium oxides, iron oxides, cobalt blue, cobalt chrome blue, cobalt nickel gray, Manganese blue, manganese violet, molybdate orange, molybdate red, nickel antimony titanate, ultramarine blue, and metal sulfides such as antimony trisulfide, cadmium sulfide, cadmium sulfoselenides, zirconium silicates, zirconium vanadium blue, zirconium praseodym yellow.

Examples of organic pigments are anthraquinone, azo, azomethine, benzanthrone, quinacridone, quinophthalone, dioxazine, flavanthrone, indanthrone, isoindoline, isoindolinone, methine, perinone, perylene, phthalocyanine, Pyranthrone, Pyrrolopyrrol-, Thioindigopigmente and metal complexes of z. As azo, azomethine, methine dyes or metal salts of azo compounds.

Suitable polymer-soluble dyes are, for example, disperse dyes, such as those of the anthraquinone series, for example alkylamino, amino, arylamino, cyclohexylamino, hydroxy, hydroxyamino or phenylmercaptoanthraquinones, and metal complexes of azo dyes, in particular 1: 2 chromium or cobalt complexes of monoazo dyes , as well as fluorescent dyes, for example those from the benzthiazole, coumarin, oxarin, or thiazine series.

The polymer-soluble dyes can also be used in combinations with fillers and / or pigments, in particular with inorganic pigments such as titanium dioxide.

Pigments and / or polymer-soluble dyes can be used. The dyes or pigments used in the case of coloring molding compositions which are to be laser translucent, of course, have no or only a very low absorption in the NIR spectral range and should be compatible with the thermoplastic polymers used according to the invention be compatible and do not significantly affect their mechanical or other properties.

Suitable pigment additives are, for example, fatty acids having at least 12 carbon atoms, such as behenic acid or stearic acid, their amides, salts or esters, such as aluminum stearate, magnesium stearate, zinc stearate or magnesium behenate, and quaternary ammonium compounds, such as tri- (C 1 -C 4) -alkylbenzylammonium salts, waxes such as polyethylene wax, resin acids such as abietic acid, rosin soap, hydrogenated or dimerized rosin, C12-C18 paraffin disulfonic acids or alkylphenols.

Preference is given to dyes of the pyrazolone, perinone and anthraquinone type, furthermore of the methine, azo and coumarin type.

Likewise preferred are the metal-containing pigments, such as the inorganic pigments and the metal complexes of azo, azomethine or methine dyes, azomethine, quinacridone, dioxazine, isoindoline, isoindolinone, perylene, phthalocyanine, pyrrolopyrrole and thioindigo Colorants and bismuth vanadate.

As nucleating agents, e.g. Calciumphenylphosphinat, lithium chloride, sodium phenylphosphinate, alumina, silica, barium sulfate, montmorillonite and preferably talc can be used.

In the case of impact modifiers (elastomer modifiers, modifiers) are generally copolymers which are preferably composed of at least two of the following monomers: ethylene, propylene, butadiene, isobutene, isoprene, chloroprene, vinyl acetate, styrene, acrylonitrile and acrylic or methacrylic acid ester with 1 to 18 C atoms in the alcohol component.

Known flame retardants in polyamides are, for example, halogen compounds, red phosphorus, organic phosphorus and nitrogen compounds or mineral flame retardants, such as e.g. Magnesium hydroxide.

• C) 5 bis 70 Gew.-% bezogen auf die Gesamtmenge an Polyamidformmasse Füllstoffe und/oder Verstärkungsstoffe, bevorzugt Minerale, synthetische Fasern, Glasfasern, Whisker oder Kohlenstofffasern, besonders bevorzugt Glasfasern enthalten.
  In einer weiteren bevorzugten Ausführungsform können die erfindungsgemäßen Polyamidformmassen zusätzlich zu den Komponenten A), B) und/oder anstelle für C) noch
• D) 0,1 - 70 Gew.-% weitere Additive und Hilfsstoffe, bevorzugt Flammschutzmittel, Elastomermodifikatioren, Farbmittel, Gleit- und Entformungsmittel oder Nukleierungsmittel enthalten.

In a preferred embodiment, the polyamide molding compositions according to the invention can therefore in addition to the components A) and B)

• C) 5 to 70 wt .-% based on the total amount of polyamide molding compound fillers and / or reinforcing materials, preferably minerals, synthetic fibers, glass fibers, whiskers or carbon fibers, particularly preferably glass fibers.
  In a further preferred embodiment, the polyamide molding compositions according to the invention can be used in addition to components A), B) and / or instead of C)
• D) 0.1 to 70 wt .-% further additives and auxiliaries, preferably flame retardants, Elastomermodifikatioren, colorants, lubricants and mold release agents or nucleating agents.

Examples: Inventive starting materials:

• Monomethyl succinate, Aldrich, Milwaukee, USA
• Pentaerythritol tetrasuccinate according to DE-A 2 411 480
• Dipentaerythritol hexasuccinate according to WO 2005 090441 A1

Non-inventive starting materials:

• Sebacic acid, Aldrich, Milwaukee, USA
• Tris (aminocaproic acid) triazine (TACT) according to Nestler, Fürst, J. Prakt. Chem. 1963 4 (22), 173
• Cyclohexanone tetrapropionic acid (CHTP) according to Bruson, Riener, J. Am. Chem. Soc., 1942, 64, 2850

compounding

In all examples and comparative examples, polyamide molding compositions are prepared in the following manner:

Polyamide-6 resin and the other additives are mixed and melted in a continuous twin-screw extruder (Werner & Pfleiderer ZSK 32). Glass fibers are dosed into the melt via a second metering funnel. The cylinder temperatures are chosen so; that melt temperatures of 260 to 300 ° C are maintained. The melt strand is introduced into water, granulated and dried. The molding compositions are used to determine the relative solution viscosity of the polyamide resin in m-cresol. From the molding compositions test specimens for the mechanical tests are produced on an injection molding machine. During the injection molding process, the filling pressure required for the production of the tension rods is determined. The measurement of the filling pressure takes place during spraying of the standard test specimen for the tensile test via a pressure sensor near the sprue on the injection mold. The pressure at the discontinuity in the mold internal pressure curve is determined between the shallower pressure rise during the mold filling phase and the steeper rise during the compression phase of the melt. The following tests are carried out on the test specimens obtained: Tensile test to ISO 527, bending test to ISO 178, impact test to Izod ISO 180 1U. Yellowness index according to ASTM E313. To determine the flowability, an 8 x 20 mm flow spiral is injected and the flow path is determined in cm. In addition, the test specimens determine the relative solution viscosity (RV) of the polyamide resin in m -cresol. (1.0% solution, 25 ° C, ISO 307: 2003)

Comparative Example 1: Preparation of polyamide molding compounds from a polyamide-6 resin having a relative solution viscosity of 2.9 in m -cresol (polyamide resin having a conventional viscosity):

The following are used: Polyamide 6 of relative solution viscosity 2.9 in m -cresol ^(® Durethan B29, Lanxess Germany GmbH): 69.6% by weight Glass fibers (CS 7928, Lanxess Deutschland GmbH): 30% by weight Nucleating agent (microtalkum) 0.2% by weight Mold release agent (montan ester wax) 0.2% by weight

Comparative Example 2 Preparation of Polyamide Molding Polyamide Resins with a Relative Solution Viscosity of 2.6 in m Cresol (about 10% Reduced Relative Solution Viscosity in Comparison to Comparative Example 1)

The following are used: Polyamide 6 of relative solution viscosity 2.6 in m -cresol (Durethan ^® B26, Lanxess Germany GmbH): 69.6% by weight Glass fibers (CS 7928, Lanxess Deutschland GmbH): 30% by weight Nucleating agent (microtalkum) 0.2% by weight Mold release agent (montan ester wax) 0.2% by weight

Comparative Example 3 Attempt to Produce Easy Flow Polyamide Molding Compositions from a Polyamide Resin of Conventional Relative Solution Viscosity and 0.5% by Weight of Triaminocaproic Acid Triazine (TACT)

The following are used: Polyamide 6 of relative solution viscosity 2.9 in m -cresol ^(® Durethan B29, Lanxess Germany GmbH): 69.1% by weight Triaminocaproic acid triazine (TACT) 0.5% by weight Glass fibers (CS 7928, Lanxess Deutschland GmbH): 30% by weight Nucleating agent (microtalkum) 0.2% by weight Mold release agent (montan ester wax) 0.2% by weight

Comparative Example 4 Attempt to Produce Easy-flowing Polyamide Molding Compositions from a Polyamide Resin of Conventional Relative Solution Viscosity and 0.5% by Weight of Cyclohexanone Tetrapropionic Acid (CHTP)

The following are used: Polyamide 6 of relative solution viscosity 2.9 in m -cresol ^(® Durethan B29, Lanxess Germany GmbH): 69.1% by weight Cyclohexanontetrapropionsäure (CHTP) 0.5% by weight Glass fibers (CS 7928, Lanxess Deutschland GmbH): 30% by weight Nucleating agent (microtalkum) 0.2% by weight Mold release agent (montan ester wax) 0.2% by weight

Comparative Example 5 Attempt to Produce Easy-flowing Polyamide Molding Compositions from a Polyamide Resin of Conventional Relative Solution Viscosity and 0.5% by Weight Sebacic Acid (SEBS)

The following are used: Polyamide 6 of relative solution viscosity 2.9 in m -cresol ^(® Durethan B29, Lanxess Germany GmbH): 69.1% by weight Sebacic acid (SEBS) 0.5% by weight Glass fibers (CS 7928, Lanxess Deutschland GmbH): 30% by weight Nucleating agent (microtalkum) 0.2% by weight Mold release agent (montan ester wax) 0.2% by weight

Example 1 Production of Easy-Flowing Polyamide Molding Compositions from a Polyamide Resin of Conventional Relative Solution Viscosity and 0.5% by Weight of Pentaerythritol Tetrasuccinate (PTS)

The following are used: Polyamide 6 of relative solution viscosity 2.9 in m -cresol ^(® Durethan B29, Lanxess Germany GmbH): 69.1% by weight Pentaerythritol tetrasuccinate (PTS) 0.5% by weight Glass fibers (CS 7928, Lanxess Deutschland GmbH): 30% by weight Nucleating agent (microtalkum) 0.2% by weight Mold release agent (montan ester wax) 0.2% by weight

Example 2 Production of Easy Flowing Polyamide Molding Compounds from a Polyamide Resin of Conventional Relative Solution Viscosity and 0.5% by Weight of Dipentaerythritol Hexasuccinate (DPHS)

The following are used: Polyamide 6 of relative solution viscosity 2.9 in m -cresol ^(® Durethan B29, Lanxess Germany GmbH): 69.1% by weight Dipentaerythritol tetrasuccinate (DPHS) 0.5% by weight Glass fibers (CS 7928, Lanxess Deutschland GmbH): 30% by weight Nucleating agent (microtalkum) 0.2% by weight Mold release agent (montan ester wax) 0.2% by weight

Example 3 Production of Easy Flowing Polyamide Molding Compositions from a Polyamide Resin of Conventional Relative Solution Viscosity and 0.35% by Weight of Succinic Monomethyl Ester (BMMS)

Polyamide 6 of relative solution viscosity 2.9 in m -cresol ^(® Durethan B29, Lanxess Germany GmbH): 69.25% by weight Succinic acid monomethyl ester (BMMS) 0.35% by weight Glass fibers (CS 7928, Lanxess Deutschland GmbH): 30% by weight Nucleating agent (microtalkum) 0.2% by weight Mold release agent (montan ester wax) 0.2% by weight

Results:

V.Bsp. 1 V.Bsp. 2 V.Bsp. 3 V.Bsp. 4 V.Bsp. 5 Ex.1 Ex.2 EX3 R. V. of the polyamide resin used 2.90 2.60 2.90 2.90 2.90 2.90 2.90 2.90 R. V. of the polyamide resin after compounding 2.77 2.53 2.60 2.64 2.57 2.54 2.49 2.58 R. V. of the polyamide resin after injection molding 2.77 2.53 2.46 2.44 2.41 2.49 2.47 2.54 Change of R.V. at compounding -2.7% -4.5% -10.3% -9.0% -11.4% -12.4% -14.1% -11.0% Change of R.V. during injection molding 0% 0% -5.4% -7.6% -6.2% -2.0% -0.8% -1.6% Injection molding pressure [bar] 254 190 182 164 152 192 188 196 Length of the flow spiral [cm] 50 60 63 66 71 61 61 61 Impact strength [kJ / m ² ] 79 68 59 57 58 66 67 66 Yellowness index 30 31 34 35 37 28 28 31 RV = relative solution viscosity

From the results it can be seen that with the succinic acid monoesters according to the invention from Examples 1 to 3 from a polyamide resin of conventional viscosity easily flowing molding compositions can be produced which lead to moldings with the same mechanical and rheological properties, as they normally only with easily flowing molding compositions, made a polyamide resin of reduced viscosity (Comparative Example 2) can be achieved. Thermal damage also does not occur, as shown by the Yellowness Index. If this is attempted with other acid compounds (Comparative Examples 3 to 5), then molding compositions are obtained which show markedly poorer properties, in particular with regard to toughness and yellowness values.

Claims (9)

1. Use of monoesters of succinic acid as molecular-weight-reducing additive for improving flowability during the production of polyamide moulding compositions.
2. Use according to Claim 1, characterized in that the monoesters of succinic acid used comprise those with mono- or polyhydric alcohols.
3. Use according to Claim 1 or 2, characterized in that the monoesters of succinic acid used comprise monoethyl succinate, monopropyl succinate, ethylene glycol disuccinate, propylene glycol disuccinate, butylene glycol disuccinate, glycerol trisuccinate, pentaerythritol tetrasuccinate, dipentaerythritol hexasuccinate and tripentaerythritol octasuccinate.
4. Use according to Claims 1 to 3, characterized in that the polyamide moulding compositions also comprise

   C) fillers and/or reinforcing materials which are preferably minerals, synthetic fibres, glass fibres, whiskers or carbon fibres.
5. Use according to Claims 1 to 4, characterized in that the polyamide moulding compositions also comprise D) further additives and auxiliaries, preferably flame retardants, elastomer modifiers, colorants, lubricants and mould-release agents and nucleating agents.
6. Use according to Claims 1 to 5, characterized in that the amounts used of the monoesters of succinic acid are from 0.1 to 2% by weight, based on component A), polyamide.
7. Use according to Claim 4, characterized in that the amounts used of component C) are from 5 to 70% by weight, based on the total amount of polyamide moulding composition.
8. Use according to Claims 4 and 7, characterized in that component C) involves glass fibres.
9. Use according to Claim 5, characterized in that the amounts used of the further additives and auxiliaries D) are from 0.1 to 70% by weight.